A polypropylene-based resin composition is generally excellent in chemical resistance and mechanical properties and therefore is used in a wide field including packaging materials, mechanical parts, and car parts. Moreover, the development of halogen-free transparent polymer materials has been progressing in recent years due to the necessity to deal with environmental problems, and especially in the fields of sheets and films, it is required to make a polypropylene-based resin soft and transparent. Further, heat sealability, flexibility, transparency, shock resistance, and surface smoothness are desired in the medical fields, e.g., for transfusion bags and in the fields of food container-packaging materials and of packaging for clothes. However the polypropylene-based resin composition is inferior in these properties and the use of the polypropylene-based resin composition in these fields has been limited in some cases. In order to solve such a problem, a method involving addition of an elastomer to the polypropylene-based resin is used.
In Patent Literature 1, a composition containing: a polyolefin-based resin; and two kinds of hydrogenated block copolymers each containing a conjugated diene compound and an aromatic vinyl compound and each having a different vinyl content is disclosed, and the composition in which the hydrogenated block copolymer having the higher vinyl content is contained in a range of 10 to 20% by mass is disclosed.
In Patent Literature 2, a polypropylene-based resin composition containing: a polyolefin-based resin; and two kinds of hydrogenated block copolymers each containing a conjugated diene compound and an aromatic vinyl compound and each having a different glass transition temperature and a different content of the aromatic vinyl compound is disclosed.
In Patent Literature 3, a polyolefin-based resin composition containing: a polyolefin-based resin; an aromatic vinyl compound; a hydrogenated block copolymer having a vinyl content of 40 to 90 mol % before hydrogenation; and a polyethylene-based powder is disclosed.